The spacers are produced in a range of sizes, so there is no single "correct" size.

Ordinarily, a matched set of two "cones" with rollers, two races, and a matched pair of inside and outside spacers are supplied. Even then, the assembly must be checked for endplay under fastener load.

It is acceptible to use individual components that were not mated,... if you mate them yourself. The Factory even used to make .002" shims.